Geared cam expandable interbody implant and method of implanting same

ABSTRACT

A geared cam expandable spinal implant. Rotational motion of a rotating portion is translated into linear motion of a yoke, which moves geared cams at the distal end of the implant to mate with, and walk along, teeth of corresponding racks. The walking of the gear cam teeth along the rack teeth creates a regular rate of implant expansion, reduces initial excessive expansion force applied to the implant, and provides fine adjustment of the expansion rate and force. Spikes, pivotally mounted on the yoke, pivot outward as the implant expands, to a fully-deployed position into engagement with surfaces of adjacent vertebral bodies. The engagement between the deployed spikes and the vertebral bodies prevents inadvertent backout of the expanded implant.

FIELD OF THE INVENTION

The present invention relates to a spinal implant, and a method forimplanting the implant in a patient's disc space between two adjacentvertebral bodies. More particularly, the present invention relates to anexpandable spinal implant including geared cams, configured to expandwithin the patient's disc space, from a collapsed position to anexpanded position.

DESCRIPTION OF THE RELATED ART

Expandable spinal implants are known. Existing expandable spinalimplants use conventional “4-bar” and “crank slider” expansionmechanisms. Following insertion, while in the collapsed position, into asurgically-enhanced disc space, the existing expandable spinal implantsare expanded. The existing expandable implants have been known at leastto (1) apply an undesirable excessive initial expansion force to thedisc space, (2) apply an irregular expansion force to the disc space,(3) occasionally inadvertently back out of the disc space, and (4) lacka reliable capability for fine adjustment. Existing expandable implantsalso lack different configurations at the distal tip of the implant,which often could be advantageous, e.g., to ensure engagement betweenthe distal tip and the adjacent vertebral bodies.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an expandable spinalimplant which obviates one or more of the shortcomings of the relatedart.

It is another object of the present invention to provide an expandablespinal implant for insertion into a patient's disc space between anupper vertebral body and a lower vertebral body. The implant has aproximal end and a distal end defining a mid-longitudinal axistherebetween, and is expandable between a collapsed position, apartially-expanded position, and a fully-expanded position.

The implant includes an upper endplate. The upper endplate has aproximal end, a distal end, an outer surface, first and second sidesurfaces, and an inner surface. A portion of the inner surface includesan upper rack portion. The upper rack portion includesdownwardly-projecting teeth intermediate the proximal end and the distalend of the upper endplate, and at least one distal-mostdownwardly-projecting tooth proximate the distal end of the upperendplate. The implant further includes a lower endplate. The lowerendplate has a proximal end, a distal end, an outer surface, first andsecond side surfaces, and an inner surface. A portion of the innersurface includes a lower rack portion. The lower rack portion includesupwardly-projecting teeth intermediate the proximal end and the distalend of the lower endplate, and at least one distal-mostupwardly-projecting tooth proximate the distal end of the lowerendplate. The proximal end of the lower endplate is pivotally connectedto the proximal end of the upper endplate.

A chassis portion is mounted within the implant between the upperendplate and the lower endplate. The chassis portion has a proximal endand a distal end. The proximal end has an opening defined therein.

A yoke is movably mounted within the chassis portion. The yoke has aproximal end and a distal end. The yoke is defined by first and secondparallel spaced-apart walls extending from the proximal end to thedistal end. A distal cross-piece, transverse to the longitudinal axis,connects the distal ends of the first and second walls of the yoke.

A rotating portion is rotatably mounted within the chassis portion. Therotating portion has a proximal end and a distal end. The distal end isconfigured to contact the distal cross-piece of the yoke. The proximalend has an opening defined therein, configured to receive a distal endof an implant expansion tool.

At least one first spur gear is rotatably mounted on a distal end of oneof the first and second walls of the yoke. The at least one first spurgear has teeth configured to engage the downwardly-projecting teeth ofthe upper rack portion. At least one second spur gear is rotatablymounted on a distal end of one of the first and second walls of theyoke. The at least one second spur gear has teeth configured to engagethe upwardly-projecting teeth of the lower rack portion.

The rotating portion is configured to translate rotational motionthereof to linear motion of the yoke. The yoke translates the linearmotion to rotation of the spur gears with respect to the yoke, causingthe spur gears to walk along the upper rack gear teeth and lower rackgear teeth, respectively, toward the distal end of the implant, therebymoving the implant through the partially-expanded position. When thespur gear teeth abut against the distal-most teeth, respectively of theupper rack or the lower rack, the implant has reached the fully-expandedposition.

One or more spikes are pivotally mounted in pockets within the implant.The linear motion of the yoke pushes distal ends of the spikes intocontact with ramped surfaces defined in openings in the upper and lowerendplates. Contact with the ramped surfaces causes the one or morespikes to pivot to fully-deployed positions, with distal edges of theone or more spikes engaging the upper and lower vertebral bodies. Thisengagement between the distal edges of the one or more spikes, and theupper and lower vertebral bodies prevents the implant, in thefully-expanded position, from inadvertently backing out of the discspace.

First and second flaps are attached to the respective first and secondside surfaces of the upper endplate and the lower endplate. The flapscan be made of porous, semi-porous, or solid materials, depending on theapplication. When the implant is in the collapsed position, the flapscan either be stretched tight between the respective side surfaces, orhang loosely between the respective side surfaces. When the implant isfully expanded, the flaps are stretched tight between the respectiveside surfaces, functioning as a barrier to prevent bone graft materialfrom leaking out of the sides of the fully expanded implant.

It is a further object of the present invention to provide a method ofimplanting the expandable spinal implant described above into apatient's disc space between an upper vertebral body and a lowervertebral body. The method includes inserting the implant into asurgically-prepared disc space, in the collapsed position, using animplant insertion tool, rotating the rotating portion, defining arotational motion, translating the rotational motion of the rotatingportion into a linear motion of the yoke toward the distal end of theimplant, rotating the spur gears with respect to the yoke, therebywalking the spur gears along the projecting teeth of the respectiveupper and lower racks, and expanding the implant through thepartially-expanded position to the fully-expanded position. The linearmotion of the yoke also translates into pivotal motion of the one ormore spikes mounted in the implant. The one or more spikes pivot from acollapsed position in the implant to a fully-deployed position withdistal ends in engagement with upper and lower vertebral bodies adjacentthe disc space. The fully-deployed spikes, in engagement with the upperand lower vertebral bodies, prevent the fully-expanded implant frombacking out of the disc space. The insertion tool includes an outerhollow shaft, an inner hollow shaft configured to pass through the outershaft, and an elongated driver configured to pass through the innerhollow shaft. The elongated driver has a blunt distal end configured tocontact a portion of the implant. Application of a movement to theelongated driver is transferred to the implant, forcing the implant intothe disc space. After removal of the elongated driver, bone growthmaterial can be routed through the inner shaft and into the implant. Theone or more fully-deployed spikes, in engagement with the upper andlower vertebral bodies, prevent the fully-expanded implant frominadvertently backing out of the disc space.

These and other objects of the present invention will be apparent fromreview of the following specification and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an upper perspective view of a geared cam expandable spinalimplant in accordance with the invention, in a collapsed position;

FIG. 2 is an upper perspective view of a geared cam expandable spinalimplant in accordance with the invention, in a partially expandedposition;

FIG. 3 is an upper perspective view of a geared cam expandable spinalimplant in accordance with the invention, in a partially expandedposition;

FIG. 4 is an upper perspective view of a geared cam expandable spinalimplant in accordance with the invention, in a fully expanded position;

FIG. 5 is an upper perspective view of a geared cam expandable spinalimplant in accordance with the invention, in a fully expanded position;

FIG. 6 is an exploded parts view of a geared cam expandable spinalimplant in accordance with the invention;

FIG. 7 is an upper perspective view of a lower endplate, chassisportion, yoke, rotating portion, and spur gears, of a geared camexpandable spinal implant in accordance with the invention;

FIG. 8 is a cross-sectional side view of a geared cam expandable spinalimplant in accordance with the invention, in a collapsed position;

FIG. 9 is a cross-sectional side view of a geared cam expandable spinalimplant in accordance with the invention, in a fully-expanded position;

FIGS. 10-16 are side schematic views of a multi-stage expansionmechanism used in one preferred embodiment of a geared cam expandablespinal implant in accordance with the invention;

FIG. 17 is an upper perspective view of a geared cam expandable spinalimplant in accordance with the invention, in a collapsed position;

FIG. 18 is an upper perspective view of a geared cam expandable spinalimplant in accordance with the invention, in a fully open position;

FIG. 19 is an upper perspective view of a geared cam expandable spinalimplant in accordance with the invention, in a partially expandedposition;

FIG. 20 is an upper perspective view of a geared cam expandable spinalimplant in accordance with the invention, in a fully expanded position;

FIG. 21 is a side cross-sectional view of a geared cam expandable spinalimplant in accordance with the invention, in a partially expandedposition;

FIG. 22 is a side cross-sectional view of a geared cam expandable spinalimplant in accordance with the invention, in a fully expanded position;

FIG. 23 is an upper perspective view of another embodiment of a gearedcam expandable spinal implant in accordance with the invention, in acollapsed position;

FIG. 24 is an upper perspective view of the embodiment of FIG. 23, in afully expanded position;

FIG. 25 is an exploded parts view of a geared cam expandable implant inaccordance with the invention;

FIG. 26 is a side cross-sectional view of a geared cam expandable spinalimplant in accordance with the invention, in a collapsed position;

FIG. 27 is a side cross-sectional view of a geared cam expandable spinalimplant in accordance with the invention in a fully expanded position;

FIGS. 28 and 29 are rear views of a geared cam expandable spinal implantin accordance with the invention;

FIG. 30 is a side cross-sectional view of a geared cam expandable spinalimplant in accordance with the invention in a collapsed position;

FIG. 31 is a side cross-sectional view of a geared cam expandable spinalimplant in accordance with the invention in a fully expanded position;

FIGS. 32-34 are side schematic views of a spur gear and rack in aone-stage expansion mechanism;

FIG. 35 is an upper perspective view of a geared cam expandable spinalimplant in accordance with the invention in a collapsed position;

FIG. 36 is an upper perspective view of a geared cam expandable spinalimplant in accordance with the invention in a fully expanded position;

FIG. 37 is an upper perspective view of a geared cam expandable spinalimplant in accordance with the invention in a fully expanded position;

FIG. 38 is an upper perspective cross-sectional view of an implantinsertion tool in accordance with the invention connected to a gearedcam expandable spinal implant in accordance with the invention;

FIG. 39 is an upper perspective view of an implant insertion tool inaccordance with the invention connected to a geared cam expandablespinal implant in accordance with the invention, depicting insertion ofthe implant into a disc space;

FIG. 40 is an upper perspective cross-sectional view of an implantinsertion tool in accordance with the invention connected to a gearedcam expandable spinal implant in accordance with the invention;

FIG. 41 is an upper perspective cross-sectional view of a geared camexpandable implant attached to an implant insertion tool in accordancewith the invention;

FIG. 42 is an upper perspective cross sectional view of a geared camexpandable implant in accordance with the invention being inserted intoa disc space by an implant insertion tool in accordance with theinvention;

FIG. 43 is an upper perspective cross sectional view of a geared camexpandable implant in accordance with the invention being inserted intoa disc space by an implant insertion tool in accordance with theinvention;

FIG. 44 is an upper perspective cross sectional view of a geared camexpandable implant inserted into the disc space, following removal ofthe implant insertion tool;

FIG. 45 is an upper perspective view of a geared cam expandable implantin accordance with the invention being supported by a lower vertebralbody;

FIG. 46 is an upper perspective view depicting points of attachmentbetween a geared cam expandable implant in accordance with theinvention, and an implant insertion tool in accordance with theinvention.

FIG. 47 is a side cross-sectional view of a geared cam expandable spinalimplant in accordance with the invention;

FIG. 48 is a side cross-sectional view of a geared cam expandable spinalimplant in accordance with the invention;

FIG. 49 is a partial upper perspective view depicting a lower endplate,chassis, yoke, lower spur gear, and cylinder with circumferentialratchet teeth;

FIG. 50 is a perspective view of a geared cam expandable implant inaccordance with the invention, including deployable spikes, pivotallyattached to the implant, in a fully-expanded position;

FIG. 51 is a perspective view depicting a chassis portion, a yoke, arotating portion, spur gears, and deployable spikes pivotally attachedto the yoke, of a geared cam expandable implant in accordance with theinvention;

FIG. 52 is a side view of a geared cam expandable implant in accordancewith the invention, including deployable spikes, pivotally attached tothe implant, in a collapsed position;

FIG. 53 is a side view of a geared cam expandable implant in accordancewith the invention, including deployable spikes, pivotally attached tothe implant in a partially expanded position;

FIG. 54 is a side view of a geared cam expandable implant in accordancewith the invention, including deployable spikes, pivotally attached tothe implant, in a fully expanded position;

FIG. 55 is a side view of a geared cam expandable implant in accordancewith the invention, including deployable spikes, pivotally attached tothe implant, and including apertures defined through internal parts, ina fully expanded position;

FIG. 56 is a side view of a geared cam expandable implant in accordancewith the invention, in a collapsed position, including deployablespikes, pivotally attached to the implant, and including lateralopenings to allow flow of bone graft material out of sides of theimplant, and further including a planar portion in the upper endplate todistribute load forces, in a fully expanded position;

FIG. 57 is a front view of a geared cam expandable implant in accordancewith the invention, including flaps attached to sides of the implant, ina closed position;

FIG. 58 is an upper view of a geared cam expandable implant inaccordance with the invention, including flaps attached to sides of theimplant, in a closed position;

FIG. 59 is a side view of a geared cam expandable implant in accordancewith the invention, including flaps attached to sides of the implant, ina closed position;

FIG. 60 is a side cross-sectional view of a geared cam expandableimplant in accordance with the invention, in a collapsed position, witha bone graft insertion apparatus connected to a proximal end of theimplant;

FIG. 61 is a side cross-sectional view of a geared cam expandableimplant in accordance with the invention, in a fully expanded position,with a bone graft insertion apparatus connected to a proximal end of theimplant; and

FIG. 62 is a side cross-sectional view of a geared cam expandableimplant in accordance with the invention, in a fully expanded position,with a bone graft insertion apparatus connected to a proximal end of theimplant, and a graft insertion tube filled with bone graft materialprovided within the bone graft insertion apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A geared cam expandable spinal implant 10 is configured to be insertedin a surgically-enhanced disc space between an upper vertebral body andan adjacent lower vertebral body. The implant 10 includes a proximal end12 and a distal end 14, defining a mid-longitudinal axis L-Ltherebetween.

In one embodiment, the implant 10 includes an upper endplate 16. Asdepicted in FIGS. 6, 8, and 9, the upper endplate 16 includes a proximalend 18, a distal end 20, side surfaces 22, and an inner surface 24. Theinner surface 24 includes an upper rack portion 26, which includesdownwardly-projecting teeth 28, and a distal-most downwardly-projectingtooth 29.

In one embodiment, the implant 10 includes a lower endplate 30. Thelower endplate 30 includes a proximal end 32, a distal end 34, sidesurfaces 36, and an inner surface 38. The inner surface 38 includes alower rack portion 40, which includes upwardly-projecting teeth 42, anda distal-most upwardly-projecting tooth 43.

In one embodiment, the implant 10 includes a chassis portion 44 mountedwithin the implant between the upper endplate 16 and the lower endplate30. The chassis portion 44 includes a proximal end 46 and a distal end48. As depicted in FIGS. 7-9, 21, 22, and 46, the proximal end 46 of thechassis portion 44 is a wall perpendicular to the mid-longitudinal axisL-L, having an opening 50 defined through the wall, and one or moredepressions 52 defined in the wall proximate the opening 50. The chassisportion 44 further includes a first set of internal threads 54 definedin the opening 50 of the proximal end 46.

In one embodiment, as depicted in FIGS. 1-7, the chassis portion 44includes an arcuate portion 56 intermediate the proximal end 46 and thedistal end 48. A second set of internal threads 58 is defined on aninner surface of the arcuate portion 56.

In one embodiment, a yoke 60 is movably mounted within the chassisportion 44. The yoke 60 is defined by a first wall 62, and a parallelsecond wall 64 spaced away from the first wall 62. First wall 62 has aproximal end 66 and a distal end 68. Second wall 64 has a proximal end70 and a distal end 72. As depicted in FIGS. 6, 7, and 41-43, distalends 68 and 72 of first and second walls 62 and 64 can be connected by adistal end cross-piece 71. As depicted in FIG. 5, the yoke 60 includes aslot 74 defined in at least one of first wall 62 and second wall 64.Each slot 74 is configured to receive therein a pin 76 projecting froman inner side surface of the lower endplate 30. Insertion of the pin 76into the slot 74 assists in preventing separation of the implant 10.

In one embodiment, a rotating portion 78 is rotatably mounted within thechassis portion 44. Rotating portion 78 includes a proximal end 80, adistal end 82, and an outer surface 84, with outer threads 86 defined onthe outer surface 84. In one embodiment, as depicted in FIGS. 6, 8, 9,20-22, 25-27, 30, and 31, the distal end 82 includes a T-shapedprojection 88. The invention, however, is not limited to having aT-shaped projection at the distal end 82 of the rotating portion 78. Inone embodiment, the proximal end 80 of the rotating portion includes anopening 89, configured to receive therein a distal end of an implantexpansion tool (not shown). The invention is not limited to anyparticular configuration for the opening 89, as long as the rotatingportion 78 can be rotated by the implant expansion tool. As depicted inFIGS. 8 and 9, the opening 89 has a polygonal shape to receive apolygonal-shaped distal end of the implant expansion tool. As anotherexample, but not by way of limitation, the opening 89 could be threadedto receive a threaded distal end of the implant expansion tool.

In one embodiment, as depicted in FIG. 47-49, the threaded rotatingportion 78 has been replaced by a cylinder 164 with circumferentialratchet teeth 166, and the mating threads 54 on the arcuate portion 56have been replaced by integral pawls 168. The ratchet teeth 166 areseparated by grooves 170. The pawls 168 are allowed to flex because theyare integral with “live” springs 172 attached to the chassis portion 44.In this embodiment, as the ribbed cylinder 164 is advanced, each pawl168 advances to the next respective groove 170. In this manner, thedistal end of the cylinder 164 pushes on the yoke 60, causing the spurgears 90 and 94 to walk toward the distal end 14 of the implant 10,expanding the implant, while the pawls 168 are retained in therespective grooves 170 between the ratchet teeth 166, thereby retainingthe implant 10 in its current expanded position.

In one embodiment, a pair of first spur gears 90 is rotatably mounted tothe distal end 68 of the first wall 62 of the yoke 60, and the distalend 72 of the second wall 64 of the yoke 60, respectively. Each firstspur gear 90 includes projecting first spur gear teeth 92, configured toengage with the downwardly-projecting teeth 28 of the upper rack portion26.

In one embodiment, as depicted in FIGS. 5-7, 18, 24, 36, and 37, asecond spur gear 94 is rotatably mounted between the distal end 68 ofthe first wall 62 of the yoke 60, and the distal end 72 of the secondwall 64 of the yoke 60, respectively. As depicted in FIG. 6, the spurgears 90 and 94 are rotatably attached to the yoke 60 with a pin 98. Thesecond spur gear 94 includes projecting second spur gear teeth 96,configured to engage with the upwardly-projecting teeth 42 of the lowerrack portion 40. The invention is not limited to having two first spurgears 90 and one second spur gear 94. For example, as depicted in FIG.20, the invention can include two first spur gears 90 and two secondspur gears 94. It is also within the scope of the invention to have onefirst spur gear 90, and two second spur gears 94.

In one embodiment, as depicted in FIGS. 19 and 20, a slot 160 is definedin the side surface 36 proximate the distal end 34 of the lower endplate30, and a pin 162 is defined projecting from a second spur gear 94. Pin162 is configured to engage with slot 160, to help prevent the upper andlower endplates from separating.

In one embodiment, the rotating portion 78 rotates within the chassisportion 44, with the outer threads 86 of the rotating portion 78engaging threaded portion 58 of the chassis portion 44, until the distalend 82 of the rotating portion 78 contacts the distal cross-piece 71 ofthe yoke 60. Rotation of the rotating portion 78 is translated intolinear motion of the yoke 60 towards the distal end 14 of the implant10. Linear motion of the yoke 60 causes the first spur gears 90, and thesecond spur gears 94 to rotate. The respective first spur gear teeth 92and second spur gear teeth 96 “walk” towards the distal end 14 of theimplant 10 in the respective downwardly-projecting teeth 28 of the upperrack portion 26, and upwardly-projecting teeth 42 of the lower rackportion 40. As the teeth “walk,” the upper endplate 16 is moved awayfrom the lower endplate 30, thereby moving the implant 10 into andthrough the partially-expanded position. When the respective spur gearteeth 92 and 96 reach the respective distal-most downwardly-projectingtooth 29, or alternately the distal-most upwardly-projecting tooth 43,they can “walk” no farther towards the distal end of the implant 10, andthe implant has reached the fully-expanded position. The amount ofexpansion in the fully-expanded position is related to the length of thespur gears. As depicted in FIG. 6, the spur gears have a length S1, butdifferent spur gear lengths are possible, depending on the requirementsof an individual patient. Different amounts of full expansion, relatedto spur gear length are depicted, for example, in FIGS. 4, 5, 9, 20, and22.

In one embodiment, as depicted in FIGS. 32-34, the spur gears 90 and 94“walk” along the respective racks 26 and 40 in a one-stage expansionmovement, with the respective spur simply rolling along the respectiverack.

In one embodiment, as depicted in FIGS. 10-16, the spur gears 90 and 94“walk” along the respective racks 26 and 40 in a multi-stage expansionmovement, including the respective spur initially rolling along therespective rack, as depicted in FIGS. 10 and 11, and subsequentlypivoting in a ball and socket fashion, as depicted in FIGS. 12 and 13.As depicted in FIGS. 14-16, the circumferences of the pitch diameterstranslate along each other as the gear is advanced. This translationallows a higher angle of incidence at the starting point for the deviceas compared to a fixed-length link mechanism. The angle ofincidence/mechanical advantage starts high and decreases as the gear isadvanced, increasing as the gear advances further. The multi-stageexpansion pattern allows a constant angle of attack of the gear with therack.

In one embodiment, as depicted in FIGS. 1 and 2, the upper endplate 16includes projections 100, configured to engage a surface of the endplateof the upper vertebral body (not shown). The upper endplate 16 furtherincludes an opening 102 defined therein, configured to allow bone growthfrom bone growth material loaded in the implant 10 to pass through theopening 102 and fuse with the upper vertebral body. The upper endplate16 further includes a smooth surface 104, configured to distribute thevertebral body endplate loading. The smooth surfaces 104 can beconfigured along a majority of the length of the upper surface of theupper endplate 16, as depicted in FIGS. 1 and 2, or for only a portionof the length of the upper surface, to contact only the softercancellous-like bone off the upper vertebral body endplate.

In one embodiment, as depicted in FIGS. 8 and 9, the lower endplate 30includes projections 106 for engaging the endplate of the lowervertebral body (depicted in FIG. 45), and an opening 108 configured toallow bone growth from the bone graft material in the implant 10 to passthrough the opening 108 and fuse with the lower vertebral body.

In one embodiment, the distal end 20 of the upper endplate 16, and thedistal end 34 of the lower endplate 30 define a tip 110. The tip 110 canbe beveled, as depicted in FIG. 45; flat, as depicted in FIGS. 23 and24; or come to a central point, as depicted in FIG. 26.

In one embodiment, the tip 110 can include bone-engaging projections112. In accordance with another embodiment, the tip 110 can have noprojections. The bone-engaging projections 112 are configured to preventimplant migration as the implant 10 is expanding. The bone-engagingprojections 112 may be perpendicular to the side surfaces 22 and 36, butgenerally follow the shape of the tip 110, or they could be parallel tothe tip 110.

In one embodiment as depicted in FIGS. 35 and 36, an engaging pin 114extends from at least one spur gear 90 or 94, and is engaged in a slot116 in a side of the upper endplate 16. Engagement of the engaging pin114 in slot 116 assists in preventing the endplates 16 and 30 fromdecoupling during expansion of the implant 10.

In one embodiment, as depicted in FIGS. 35 and 36, an upper gear 118 isdefined at the proximal end 18 of the upper endplate 16, in engagementwith a lower gear 120 defined at the proximal end 32 of the lowerendplate 30. Engagement of the upper and lower proximal gears 118 and120, respectively, assists in preventing the endplates 16 and 30 fromdecoupling during expansion of the implant 10.

In one embodiment, an independent proximal expansion mechanism 122 isdefined at the proximal end 12 of the implant 10. As depicted in FIGS.28-31, 35, and 36, the proximal expansion mechanism 122 includes aproximal-end polygonal-shaped toggle 124, attached to the proximal end80 of the rotating portion 78. A pair of proximal-end pivot pins 126projects from the proximal-end toggle 124. In one embodiment, the toggle124 can have one distraction position while in another embodiment, thetoggle 124 can have progressive distraction positions. In oneembodiment, the toggle 124 can be rotated, while in another embodiment,the toggle 124 can be translated. In the embodiment where the toggle 124is rotated, the pivot pins 126 distract, using a cam-like action. In theembodiment where the toggle 124 is translated, the pivot pins 126 aredistracted by sliding along proximal ramps 128.

In one embodiment, an insertion tool 130, depicted in FIGS. 38-44 and46, includes a proximal end 132, and a distal end 134. An outer hollowcylindrical shaft 136 extends between the proximal end 132 and thedistal end 134. An inner hollow cylindrical shaft 138 extends throughthe outer shaft 136. The inner shaft 138 has a proximal end 140 and adistal end 142.

In one embodiment, as depicted in FIG. 38, a T-handle 158 is defined atthe proximal end 140 of the inner shaft 138. The T-handle 158 attachesto an elongated driver 143, which extends through the inner shaft 138.

In one embodiment, as depicted in FIGS. 42 and 43, the elongated driver143 has a blunt distal end 154.

In one embodiment, as depicted in FIG. 39, a tap cap 144 is defined atthe proximal end 140 of the inner shaft 138, attached to the driver 143.

In one embodiment, as depicted in FIG. 40, the tap cap 144 fitsremovably into a funnel 146 defined at the proximal end 140 of the innershaft 138.

In one embodiment, a handle 148 is provided, gripping an outer surfaceof the outer shaft 136. Handle 148 is configured to be held by a surgeonwhile using the insertion tool 130.

In one embodiment, as depicted in FIG. 46, the distal end 134 of theouter shaft 136 includes projecting fingers 150, configured to fit intothe depressions 52, proximate the opening 50 in the proximal end 46 ofthe chassis portion 44.

In one embodiment, as depicted in FIGS. 40 and 46, the distal end 142 ofthe inner shaft 138 includes external threads 152, configured to engagethe first set of inner threads 54 in the opening 50 of the chassisportion 44.

In one embodiment, as depicted in FIGS. 38, 39, and 42, moving theelongated driver 143, either by applying a force to the T-handle 158, orby applying a force to the tap cap 144, the elongated driver 143 ismoved through the inner shaft 138, through the opening 50 in theproximal end 46 of the chassis portion 44, and through the chassisportion 44, until the blunt proximal end opening 89 in the rotatingportion 78. Translation of the motion of the elongated driver 143 to therotating portion 78 pushes the implant 10 into the disc space. Followingremoval of the elongated driver 143 from the implant 10 and the innershaft 138, as depicted in FIG. 44, bone growth material can be insertedthrough the inner shaft 138 and into the implant 10.

In one embodiment, as depicted in FIGS. 50-54, upper spikes 174 andlower spikes 176 are pivotally connected to the walls 62 and 64 of theyoke 60. Each upper spike 174 includes a proximal end 177 pivotallyconnected to a wall of the yoke, and a distal end 178. Each lower spike176 includes a proximal end 180 pivotally connected to a wall of theyoke, and a distal end 182. Each distal end 178 includes an upperarcuate distal end portion 184 and an upper edge 185. Each distal end182 includes a lower arcuate distal end portion 186 and a lower distaledge 188.

In one embodiment, as depicted in FIG. 52, upper pockets 190 are definedwithin the implant 10 to store the upper spikes 174 when the implant 10is in the collapsed position. Likewise, lower pockets 192 are definedwithin the implant 10 to store the lower spikes 176 when the implant 10is in the collapsed position.

In one embodiment, as depicted in FIGS. 50, 52 and 53, an upper opening194 is defined in the upper endplate 16 proximate the upper pocket 190.A lower opening 196 is defined in the lower endplate 30 proximate thelower pocket 192. The upper opening 194 includes an upper ramped surface198 at a distal end thereof, and the lower opening 196 includes a lowerramped surface 200 at a distal end thereof. When the yoke 60 begins tomove in the distal direction, and the implant 10 begins to expand, theupper spikes 174 and the lower spikes 176 are simultaneously pushed bythe yoke 60 in the distal direction. Upper arcuate distal end portions184 of the upper spikes 174 are pushed into contact with the upperramped surface 198 of the upper opening 194 in the upper endplate 16,and lower arcuate distal end portions 186 of the lower spikes 176 arepushed into contact with the lower ramped surface 200 of the loweropening 196 of the lower endplate 30. The distal force applied by theyoke 60, pushing the upper arcuate distal end portions 184 of the upperspikes 174 into contact with the upper ramped surface 198 defined in thedistal end of the upper opening 194 defines a torque T (upper). Torque T(upper) forces the upper spikes 174 to pivot clockwise, through theupper opening 194. Likewise, the distal force applied by the yoke 60,pushing the arcuate distal end portions 186 of the lower spikes 176 intocontact with the lower ramped surface 200 of the lower opening 196defines a torque T (lower). Torque T (lower) forces the lower spikes 176to pivot counter-clockwise, through the lower opening 196 in the lowerendplate 30. As the implant 10 continues to expand, the upper spikes 174continue to pivot until they reach an orientation along an axis which istransverse to the mid-longitudinal axis L-L of the implant 10, with theupper edges 185 engaging the upper vertebral body. Likewise, the lowerspikes 176 continue to pivot until they reach an orientation along anaxis transverse to the mid-longitudinal axis L-L of the implant 10, withthe lower edges 188 engaging the lower vertebral body.

In one embodiment, as depicted in FIG. 55, apertures can be defined ininternal parts of the implant, for example co-axial apertures 202 andtransverse apertures 204 defined in the rotating portion 78. Theapertures 202 and 204 are configured to permit flow of bone graftmaterial therethrough as it is injected from the proximal end 46 of thechassis 44.

In one embodiment, as depicted in FIG. 55, as the yoke 60 moves in thedistal direction, deploying the upper and lower spikes 174 and 176, aco-axial aperture 206 is opened in the chassis 44 behind the proximalends 177 and 180 of the spikes 174 and 176, respectively. Co-axialaperture 206 also is configured to allow a flow of bone growth materialtherethrough.

In one embodiment, as depicted in FIG. 57, flaps 208 are attached to theright and left sides of the implant 10 (only one side shown), with upperand lower edges thereof connected between the upper endplate 16 and thelower endplate 30. The flaps 208 can be made of a porous material, asemi-porous material, or a solid material. When the implant 10 isexpanded, as depicted in FIG. 57, the flaps 208 are deployed, stretchedtightly between the upper endplate 16 and the lower endplate 30.

In one embodiment, as depicted in FIGS. 60-62, an implant 10 includes abone graft inserter 210, attachable to attachment clamps 212 provided atthe proximal end 46 of the chassis portion 44. The bone graft inserterincludes an outer tube 214 defining a lumen 216 therethrough, and ahandle 218. The attachment clamps 212 are positioned to firmly grip adistal end of the outer tube 214.

In one embodiment, as depicted in FIGS. 60-62, a graft tube 220 isprovided within the lumen 216. Bone graft material in the graft tube 220is in position to flow into the chassis portion 44 of the implant 10 viathe connection between the attachment clamps 212 and the outer tube 214.As further depicted in FIGS. 60-62, the bone graft material insertedinto the chassis portion 44 of the implant 10 can flow out of theimplant 10 via multiple small apertures (not shown) in the upper andlower endplates 16 and 30, respectively, and via the open distal end ofthe expanded implant 10.

In one embodiment, as depicted in FIGS. 58 and 59, a rigid plunger 222is provided in the lumen 216. The plunger 222 includes a head portion224 at a distal end thereof. The head portion 224 has a diameterapproximately equal to a diameter of the lumen 216. When the plunger 222slides within the lumen 216 in the distal direction, the head portion224 pushes bone graft material in the distal direction and into theproximal end 46 of the chassis portion 44.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

I claim:
 1. An expandable spinal implant for insertion into a patient'sdisc space between an upper vertebral body and a lower vertebral body,the implant having a proximal end and a distal end defining amid-longitudinal axis therebetween, and being expandable between acollapsed position, a partially-expanded position, and a fully-expandedposition, the implant comprising: an upper endplate, the upper endplateincluding a proximal end, a distal end, an outer surface, at least oneside surface, and an inner surface, a portion of the inner surfaceincluding an upper rack portion, the upper rack portion including atleast one downwardly-projecting tooth intermediate the proximal end andthe distal end of the upper endplate, and at least one distal-mostdownwardly-projecting tooth proximate the distal end of the upperendplate; a lower endplate, the lower endplate including a proximal end,a distal end, an outer surface, at least one side surface, and an innersurface, a portion of the inner surface including a lower rack portion,the lower rack portion including at least one upwardly-projecting toothintermediate the proximal end and the distal end of the lower endplate,and at least one distal-most upwardly-projecting tooth proximate thedistal end of the lower endplate, the proximal end of the lower endplatebeing pivotally connected to the proximal end of the upper endplate; achassis portion mounted within the implant between the upper endplateand the lower endplate, the chassis portion having a proximal end and adistal end, the proximal end having an opening defined therein, at leastone depression defined therein proximate the opening, a first set ofinner threads defined in the opening, and a second set of inner threadsdefined intermediate the proximal end and the distal end of the chassisportion; a yoke movably mounted within the chassis portion the yokehaving a proximal end and a distal end, and being defined by first andsecond substantially parallel spaced apart walls, each of the first andsecond spaced apart walls having a proximal end and a distal end; arotating portion rotatably mounted within the chassis portion, therotating portion having an outer surface, a proximal end and a distalend, the proximal end having an opening defined therein, the distal endbeing positioned proximate the distal end of the yoke, and threadsdefined on at least a portion of the outer surface, the threads beingengageable with the second set of inner threads in the chassis portion;at least one first spur gear rotatably mounted to at least one of thedistal ends of at least one of the first and second spaced apart wallsof the yoke, the at least one first spur gear having at least oneprojecting first spur gear tooth configured to movably engage with thedownwardly-depending teeth on the upper rack portion; at least onesecond spur gear rotatably mounted to at least one of the distal ends ofat least one of the first and second spaced apart walls of the yoke, theat least one second spur gear having at least one projecting second spurgear tooth configured to engage with the upwardly-projecting teeth onthe lower rack portion; and at least one spike pivotally attached to atleast one of the first and second spaced apart walls of the yoke;wherein the rotating portion is further configured to translaterotational motion thereof to linear motion of the yoke, the yoketranslating the linear motion to rotational motion of at least the atleast one first spur gear, thereby rotating the at least one first spurgear with respect to the yoke; wherein the rotation of the at least onefirst spur gear with respect to the yoke defines a first linear walkingmotion of the at least one projecting first spur gear tooth along thedownwardly-depending upper rack gear teeth toward the distal end of theimplant, thereby pivoting the upper endplate to at least thepartially-expanded position; and wherein the linear motion of the yokeis translated to pivotal motion of the at least one spike from acollapsed position, to a fully-deployed position transverse to themid-longitudinal axis.
 2. The expandable spinal implant of claim 1,wherein at least one of the upper endplate and the lower endplateincludes at least one projection projecting from the outer surfacethereof, the at least one projection configured to engage acorresponding endplate of the respective upper vertebral body and lowervertebral body.
 3. The expandable spinal implant of claim 1, wherein theyoke further includes at least one side surface, the at least one sidesurface having a track defined therein, the track being configured toreceive therein a peg projecting from the at least one side surface ofone of the lower endplate and the upper endplate, thereby preventingdisengagement of the upper endplate from the lower endplate.
 4. Theexpandable spinal implant of claim 1, wherein the rotation of therotating portion further translates motion to at least the at least onesecond spur gear to rotate the at least one second spur gear withrespect to the yoke, the rotation of the at least one second spur gearwith respect to the yoke defining a second linear walking motion of theat least one projecting second spur gear tooth along theupwardly-projecting lower rack gear teeth toward the distal end of theimplant, pivoting the lower endplate at least to the partially-expandedposition.
 5. The expandable spinal implant of claim 1, furthercomprising at least one pocket defined between the upper endplate andthe lower endplate configured to house the at least one spike when theimplant is in the collapsed position.
 6. The expandable spinal implantof claim 1, wherein the pivotal motion of the at least one spike to thefully-deployed position exposes at least one window defined in at leastthe chassis portion.
 7. The expandable spinal implant of claim 6,wherein the at least one window defined in at least the chassis portionis configured to allow flow of bone graft material therethrough.
 8. Theexpandable spinal implant of claim 1, wherein the rotating portion isgenerally cylindrical, and includes a set of external threads defined onan outer peripheral surface thereof.
 9. The expandable spinal implant ofclaim 8, wherein the rotating portion includes at least one aperturedefined in the outer peripheral surface, the at least one aperture beingconfigured to allow flow of bone graft material therethrough.
 10. Theexpandable spinal implant of claim 1, wherein the at least one spikepivotally attached to the one of the first and second spaced apart wallsof the yoke further comprises at least two spikes pivotally attached tothe one of the first and second spaced apart walls of the yoke.
 11. Theexpandable implant of claim 1, wherein the at least one spike pivotallyattached to the one of the first and second spaced apart walls of theyoke further comprises a first pair of spikes pivotally attached to thefirst wall of the yoke, and a second pair of spikes pivotally attachedto the second wall of the yoke.
 12. The expandable spinal implant ofclaim 1, further comprising an upper gear mounted proximate the proximalportion of the upper endplate, and a lower gear mounted proximate theproximal portion of the lower endplate, the lower gear pivotallyengaging the upper gear, the engagement of the upper gear and the lowergear preventing disengagement of the upper endplate from the lowerendplate.
 13. The expandable spinal implant of claim 1, wherein at leastthe upper rack portion includes a distal-most downwardly-depending upperrack gear tooth, configured to stop at least the walking motion of theat least one first spur gear along the downwardly depending upper rackgear teeth toward the distal end of the implant, thereby moving theupper endplate away from the lower endplate toward the fully expandedposition.
 14. The expandable spinal implant of claim 1, wherein at leastthe lower rack portion includes a distal-most upwardly-projecting lowerrack gear tooth, configured to stop at least the walking motion of theat least one second spur gear along the upwardly-projecting lower rackgear teeth toward the distal end of the implant, thereby moving theupper endplate away from the lower endplate toward the fully expandedposition.
 15. The expandable spinal implant of claim 1, furthercomprising at least one opening defined in at least one of the upperendplate and the lower endplate, the at least one opening beingconfigured for the at least one spike to pass therethrough when the atleast one spike pivots to the fully-deployed position.
 16. Theexpandable spinal implant of claim 15, wherein the at least one openingincludes a proximal end, a distal end, and a ramped portion defined atthe distal end, the ramped portion being positioned to contact anarcuate portion defined on a distal end of the at least one spike,wherein the contact between the ramped portion and the arcuate portiondefines a torque, the torque pivoting the at least one spike to thefully-deployed position.
 17. The expandable spinal implant of claim 1,wherein a distal edge portion of the at least one spike, in thefully-deployed position, is configured to contact at least one of theupper vertebral body and the lower vertebral body and preventinadvertent backout of the implant from the disc space.
 18. A kit forinserting an expandable spinal implant into a patient's disc spacebetween an upper vertebral body and a lower vertebral body, the kitcomprising: the implant, the implant comprising: an upper endplate, theupper endplate including a proximal end, a distal end, an outer surface,at least one side surface, and an inner surface, a portion of the innersurface including an upper rack portion, the upper rack portionincluding at least one downwardly-projecting tooth intermediate theproximal end and the distal end of the upper endplate, and at least onedistal-most downwardly-projecting tooth proximate the distal end of theupper endplate; a lower endplate, the lower endplate including aproximal end, a distal end, an outer surface, at least one side surface,and an inner surface, a portion of the inner surface including a lowerrack portion, the lower rack portion including at least oneupwardly-projecting tooth intermediate the proximal end and the distalend of the lower endplate, and at least one distal-mostupwardly-projecting tooth proximate the distal end of the lowerendplate, the proximal end of the lower endplate being pivotallyconnected to the proximal end of the upper endplate; a chassis portionmounted within the implant between the upper endplate and the lowerendplate, the chassis portion having a proximal end and a distal end,the proximal end having an opening defined therein, at least onedepression defined therein proximate the opening, a first set of innerthreads defined in the opening, and a second set of inner threadsdefined intermediate the proximal end and the distal end of the chassisportion; a yoke movably mounted within the chassis portion, the yokehaving a proximal end and a distal end, and being defined by first andsecond substantially parallel spaced apart walls, each of the first andsecond spaced apart walls having a proximal end and a distal end; arotating portion rotatably mounted within the chassis portion, therotating portion having an outer surface, a proximal end, and a distalend, the proximal end having an opening defined therein, the distal endbeing positioned proximate the distal end of the yoke, and threadsdefined on at least a portion of the outer surface, the threads beingengageable with the second set of inner threads in the chassis portion;at least one first spur gear rotatably mounted to at least one of thedistal ends of at least one of the first and second spaced apart wallsof the yoke, the at least one first spur gear having at least oneprojecting first spur gear tooth configured to movably engage with thedownwardly-depending teeth on the upper rack portion; at least onesecond spur gear rotatably mounted to at least one of the distal ends ofat least one of the first and second spaced apart walls of the yoke, theat least one second spur gear having at least one projecting second spurgear tooth configured to engage with the upwardly-projecting teeth onthe lower rack portion; and at least one spike pivotally attached to oneof the first and second spaced apart walls of the yoke; wherein therotating portion is further configured to translate rotational motionthereof to linear motion of the yoke, the yoke translating the linearmotion to rotational motion of at least the at least one first spurgear, thereby rotating the at least one first spur gear with respect tothe yoke; wherein the rotation of at least the at least one first spurgear with respect to the yoke defines a first linear walking motion ofthe at least one projecting first spur gear tooth along thedownwardly-depending upper rack gear teeth toward the distal end of theimplant, thereby pivoting the upper endplate to at least thepartially-expanded position; and wherein the linear motion of the yoketranslates to pivotal motion of the at least one spike, from a collapsedposition to a fully-deployed position transverse to the mid-longitudinalaxis; and an insertion tool attachable to the proximal end of theimplant.
 19. A method of implanting an expandable spinal implant into apatient's disc space between an upper vertebral body and a lowervertebral body, the method comprising: utilizing the expandable spinalimplant, the implant having a proximal end and a distal end defining amid-longitudinal axis therebetween, and being expandable between acollapsed position, a partially-expanded position, and a fully-expandedposition, the implant comprising: an upper endplate, the upper endplateincluding a proximal end, a distal end, an outer surface, at least oneside surface, and an inner surface, a portion of the inner surfaceincluding an upper rack portion, the upper rack portion including atleast one downwardly-projecting tooth intermediate the proximal end andthe distal end of the upper endplate, and at least one distal-mostdownwardly-projecting tooth proximate the distal end of the upperendplate; a lower endplate, the lower endplate including a proximal end,a distal end, an outer surface, at least one side surface, and an innersurface, a portion of the inner surface including a lower rack portion,the lower rack portion including at least one upwardly-projecting toothintermediate the proximal end and the distal end of the lower endplate,and at least one distal-most upwardly-projecting tooth proximate thedistal end of the lower endplate, the proximal end of the lower endplatebeing pivotally connected to the proximal end of the upper endplate; achassis portion mounted within the implant between the upper endplateand the lower endplate, the chassis portion having a proximal end and adistal end, the proximal end having an opening defined therein, at leastone depression defined therein proximate the opening, a first set ofthreads defined in the opening, and a second set of inner threadsdefined intermediate the proximal end and the distal end of the chassisportion; a yoke movably mounted within the chassis portion, the yokehaving a proximal end and a distal end, and being defined by first andsecond substantially parallel spaced apart walls, each of the first andsecond spaced apart walls having a proximal end and a distal end; arotating portion rotatably mounted within the yoke, the rotating portionhaving an outer surface, a proximal end and a distal end, the proximalend having an opening defined therein, the distal end being positionedproximate the distal end of the yoke, and threads defined on at least aportion of the outer surface, the threads being engageable with thesecond set of inner threads on the chassis portion; at least one firstspur gear rotatably mounted to at least one of the distal ends of atleast one of the first and second spaced apart walls of the yoke, the atleast one first spur gear having at least one projecting first spur geartooth configured to movably engage with the downwardly-projecting rackteeth on the upper rack portion; at least one second spur gear rotatablymounted to at least one of the distal ends of at least one of the firstand second spaced apart walls of the yoke, the at least one second spurgear having at least one projecting second spur gear tooth configured toengage with the upwardly-projecting teeth on the lower rack portion; andat least one spike pivotally attached to at least one of the first andsecond spaced apart walls of the yoke; wherein the rotating portion isfurther configured to translate rotational motion thereof to linearmotion of the yoke, the yoke translating the linear motion to rotationalmotion of at least the at least one first spur gear, thereby rotatingthe at least one first spur gear with respect to the yoke; wherein therotation of the at least one first spur gear with respect to the yokedefines a first linear walking motion of the at least one projectingfirst spur gear tooth along the downwardly-projecting teeth of the upperrack portion toward the distal end of the implant, thereby pivoting theupper endplate to at least the partially-expanded position; and whereinthe linear motion of the yoke is further translated to pivotal motion ofthe at least one spike from a collapsed position to a fully-deployedposition transverse to the mid-longitudinal axis; inserting the implant,in the collapsed position, into the disc space between the uppervertebral body, and the lower vertebral body with an insertion tool;rotating the rotating portion, defining the rotational motion;translating the rotational motion of the rotating portion into thelinear motion of the yoke toward the distal end of the implant;translating the linear motion of the yoke into rotational motion of atleast the at least one first spur gear, and into pivotal motion of theat least one spike; rotating the at least one first spur gear withrespect to the yoke; walking the at least one first spur gear along thedownwardly-projecting teeth of the upper rack portion toward the distalend of the implant; translating the linear motion of the yoke into therotational motion of at least the at least one second spur gear; walkingthe at least one second spur gear along the upwardly-projecting teeth ofthe lower rack portion toward the distal end of the implant; reachingthe fully-expanded position when one of the at least one first spur gearcontacts the at least one distal-most projecting tooth on the upper rackportion, and the at least one second spur gear contacts the at least onedistal-most projecting tooth on the lower rack portion; and pivoting theat least one spike to the fully-deployed position transverse to themid-longitudinal axis and into an engagement with at least one of theupper vertebral body and the lower vertebral body.
 20. The method ofclaim 19, wherein the translating the linear motion of the yoke intopivotal motion of the at least one spike includes forcing an arcuatedistal end portion of the at least one spike into contact with a rampeddistal end surface of an opening in one of the upper endplate and thelower endplate, the contact between the arcuate distal end portion andthe ramped distal end surface defining a torque, the torque pivoting theat least one spike to the fully deployed position.
 21. The method ofclaim 20, wherein the engagement of the at least one spike with the oneof the upper vertebral body and the lower vertebral body prevents theimplant, in the fully-expanded position, from inadvertently backing outof the disc space.